1. Optical angular momentum in a rotating frame
- Author
-
Speirits, Fiona C., Lavery, Martin P. J., Padgett, Miles J., and Barnett, Stephen M.
- Subjects
Physics ,Angular momentum ,genetic structures ,business.industry ,Physics::Optics ,Rotational transition ,Specific relative angular momentum ,Atomic and Molecular Physics, and Optics ,symbols.namesake ,Optics ,Total angular momentum quantum number ,Angular momentum of light ,Angular momentum coupling ,symbols ,Orbital angular momentum of light ,sense organs ,business ,Doppler effect - Abstract
It is well established that light carrying orbital angular momentum (OAM) can be used to induce a mechanical torque causing an object to spin. We consider the complementary scenario: will an observer spinning relative to the beam axis measure a change in OAM as a result of their rotational velocity? Remarkably, although a linear Doppler shift changes the linear momentum of a photon, the angular Doppler shift induces no change in the angular momentum. Further, we examine the rotational Doppler shift in frequency imparted to the incident light due to the relative motion of the beam with respect to the observer and consider what must happen to the measured wavelength if the speed of light c is to remain constant. We show specifically that the OAM of the incident beam is not affected by the rotating observer and that the measured wavelength is shifted by a factor equal and opposite to that of the frequency shift induced by the rotational Doppler effect.
- Published
- 2014